The invention relates to a molding or casting apparatus, and more particularly to a system in such an apparatus for compacting sand about a molding pattern in a mold flask.
In a lost foam casting process, the mold pattern which forms the desired molding cavity in the sand is a foam mold pattern that vaporizes when contacted by molten metal so that it need not be removed from the sand before casting. Since it is not necessary to remove the foam mold pattern from the sand before casting, the mold flask need not be separable into two parts, the cope and the drag, and the mold pattern can have a more complicated configuration than with conventional cope and drag flasks.
A lost foam casting process includes the steps of placing the foam mold pattern in the mold flask, compacting sand around the mold pattern, and pouring molten metal into the foam mold pattern. The molten metal causes the foam mold pattern to vaporize, and when the metal cools, the casting is removed from the sand.
Because the sand must be tightly compacted around the mold pattern in the flask, and because of the complicated mold pattern configurations permissible with a lost foam casting process, it is desirable to have a system which will facilitate sand migration and will compact the sand around the mold pattern to high sand pressure. Prior sand compaction systems do not provide the desired sand migration or sand pressure.
Prior systems vibrate the flask vertically from the top or bottom, or horizontally from the flask base with either multi- or unidirectional forces, or with a combination of these methods. Other prior systems provide a vibrator attached to a side panel of the flask to vibrate only the panel, causing localized response of the sand to the vibration.
Attention is directed to the following U.S. patents which disclose molding apparatus and vibrating apparatus:
Fewel U.S. Pat. No. 4,288,165, issued Sept. 8, 1981; PA0 Olson U.S. Pat. No. 3,812,625, issued May 28, 1974; PA0 Dupre et al. U.S. Pat. No. 3,767,168, issued Oct. 23, 1973; PA0 Varnum et al. U.S. Pat. No. 3,724,819, issued Apr. 3, 1973; PA0 Shaw U.S. Pat. No. 3,425,670, issued Feb. 4, 1969; PA0 Corbin, Jr. U.S. Pat. No. 2,112,830, issued Apr. 15, 1938.